Exhaust emission purifying device

ABSTRACT

Improvements in an air injection type exhaust emission purifying device for a gasoline engine, the improvements consisting of an air pump driven by the engine for supplying air to the exhaust port of each cylinder to cause an oxidizing reaction between the air and hot exhaust gases, and at least one sparking or heating plug provided in an exhaust manifold to fire and burn a good mixture of air and highly dense unburned hydrocarbon resulting from the misfiring caused during the deceleration of the engine, thereby preventing the occurrence of afterburn noises and minimizing the quantity of air required and accordingly reducing the capacity of the air pump and power consumption of the engine.

United States Patent Ito et al. [451 Apr. 11, 1972 [54] EXHAUST EMISSION PURIFYING 2,937,490 5/1960 Calvert ..60/30 DEVICE 3431333 37322 E""'"' l annarino [72] Inventors: Mikfii Ito, Nagoya; Kenji Yamada, Kariya; 3 314 230 4/19 7 Vanderpoel ofJaPa" 3,392,523 7/1968 Hyde [73} Assignee: Nippondenso Kabushiki Kaisha, Aichi- 3,401,518 9/1968 McWhirter ..60/30 ken, Japan E D l H Primary xamineroug as art [221 Med: 1970 Attorney-Cushman, Darby & Cushman [21] App]. No.: 31,247

[57] ABSTRACT [30] Foreign Application Priorit Data Improvements in an air injection type exhaust emission purifying device for a gasoline engine, the improvements consisting Sept. 12, 1969 Japan ..44/875 16 of an air pump driven by the engine for Supplying air to the July 16, 1969 Japan ..44/67707 haust p of each cylinder to cause an oxidizing reaction between the air and hot exhaust gases, and at least one spark- 52 U.S. Cl ..60/294, 60/298, tag/33055, ing or heating plug provided in an exhaust manifold to fire and 51 1 Cl F01 3/14 burn a good mixture of air and highly dense unburned q a hydrocarbon resulting from the misfiring caused during the re 0 earc deceleration ofthe engine, thereby preventing the occurrence of afterburn noises and minimizing the quantity of air required [56] Rem-ewes cued and accordingly reducing the capacity of the air pump and UNITED STATES PATENTS power consumption of the engine.

2,771,736 1 1/1956 McKinley ..60/30 R 11 Claims, 6 Drawing Figures PATENTEDAPR 11 I972 3,654,763

sum 1 OF 2 Ox 0 /m/n) INVENTORJ Mmu 1T0 (5M1 YnHflnH lmzuo uwn BY ATTORNEY! PATENTEBAPR n 1972 3, 654, 763

SHEET 2 OF 2 INVENTORS MlrlJI 1T0 KEA/J/ DMD/I mum Mann BY MMQMM flMJMM,

ATTORNEYS EXHAUST EMISSION PURIFYING DEVICE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an exhaust emission purifying device, and more particularly to such a device for oxidizing and denaturing the harmful unburned exhaust products such as hydrocarbon, carbon monoxide, etc. from a gasoline engine.

2. Description of the Prior Art As an exhaust emission purifying device of the described type there is known a device of the air injection type widely used in the United States, which is excellent in durability and low in maintenance cost. In this known device, air as secondary air is injected from an air pump driven by the engine into the exhaust port of each cylinder where the air is sufficiently accumulated, then harmful unburned exhaust products discharged just after combustion through an opened exhaust valve are oxidized when they are mixed with the accumulated air, whereby the gas-air mixture is sufficiently combusted to reduce unburned hydrocarbon and carbon monoxide emission. Except during the idling and deceleration of the engine, the density of such harmful unburned exhaust products is so low that it can readily be reduced below an allowable limit to comply with anti-pollution regulations by adjusting the intake system of the engine such as carburetor. Therefore, the quantity of air required to purify the exhaust emission can be quite small. However, as shown in FIG. 3 in which the ordinate represents the quantity Q of air discharged from the air pump and the abscissa represents the number of revolutions N of the engine, most of the air is let out of the relief valve for the pumping performance indicated by a dotted curve a if the number of revolutions N of the engine exceeds about 1,000 r.p.m., thus resulting in a reduced quantity of air discharged into the exhaust port of the cylinder as indicated by a solid curve b which means a great loss of air.

In contrast, during the idling of the engine, a greater quantity of secondary air is required for a unit quantity of exhaust gases (for example, 100 liter/min. of secondary air is required per 500 r.p.m. of the engine). This means that the air pump directly driven from the engine must be large in size and capacity to supply the required great quantity of air because the maximum number of revolutions of such an air pump cannot be large. Also, during the high-speed operation of the engine, the power consumption of the engine becomes very great even if most of the air from the air pump is discharged into the atmosphere so as to reduce the load.

Furthermore, during the deceleration of the engine, the airfuel ratio is so greatly reduced (that is, the fuel in the gases becomes of such high density) that misfiring occurs in the cylinders, and it is well-known that the colder the engine is, the longer the misfiring persists. With the known gas purifying device of the above-described type, the unburned hydrocarbon discharged into the exhaust port of the cylinder and exhaust manifold and further into the exhaust pipe are accumulated therein in a state ready to be fired by mixing with the secondary air. Therefore, if normal firing and combustion of the engine take place in the course of deceleration, the combusted exhaust gases provided thereby serve as a pilot fire upon opening of the exhaust valve to thereby cause the accumulated gases to be explosively combusted with a great noise, and is called afterburn." For this reason, according to the prior art, and anti-afterburn valve is used to supply air to the intake manifold of the engine for 2 to 3 seconds at the initial stage of deceleration so as to increase the air-fuel ratio to prevent any misfiring from occurring within the cylinders and accordingly prevent the occurrence of afterbum. However, especially under cold weather conditions which require a substantial length of time for the engine to be sufficiently warmed up, the intake gas of the engine will become a greatly enriched mixture if the accelerator pedal is released to change over the speed change gear or to decelerate the engine before the engine is sufficiently warmed up. In such a case, therefore, it is necessary to open the anti-afterbum valve for a long time and to supply the air from the air pump to intake manifold in order to hold a good mixture of intake gas. This will, however, cause an excessive quantity of air to be supplied to the intake manifold of the engine after the engine has been warmed up, and such an excessive air supply will in turn deteriorate the gas purifying performance. Thus, the anti-afterburn valve now in use cannot sufficiently prevent the afterbum from occurring during the warming-up of the engine under cold weather conditions and this raises an unsolved problem in the air injection system. This problem will also occur in the case of a manifold thermal reaction which supports the exhaust gas in an exhaust manifold in high temperature and promotes oxidation of exhaust gas by injecting secondary air, too.

Another exhaust emission purifying device according to the prior art employs the direct flame afterbumer system whereby exhaust gases mixed with secondary air are fired and combusted in a combustion chamber provided intermediately in the exhaust pipe. In this device, a heat exchange must be provided because the exhaust gases are reduced in temperature by the air mixed therewith, and even if the heat exchanger is of a high efficiency, it is likely to be experienced that necessary conditions for firing the gases cannot be met in terms of the temperature of the exhaust gases, density of the harmful uncombusted emissions, etc. during the idling and deceleration of the engine. In addition, the heat exchanger and combustion chamber disposed intermediately of the exhaust pipe provide a higher exhaust resistance which acts to deteriorate the performance of the engine, and this further leads to the necessity of employing bypass means to compensate for such greater exhaust resistance.

SUMMARY OF THE INVENTION It is an object of-the present invention to overcome the above-mentioned drawbacks inherent to the prior art and to provide a very useful exhaust emission purifying device which comprises an air pump driven from an engine for discharging air into a portion adjacent to the exhaust valve of each cylinder 'so as to effect an oxidizing reaction with hot exhaust gases, and at least one sparking plug provided in the manifold portion of the device to immediately fire and burn a good mixture of air and highly dense unburned exhaust gases resulting from the misfiring caused during the deceleration of the engine. According to the present invention, the quantity of air required to purify the exhaust gases can be reduced and the unburned gases ready to be burnt are prevented from accumulating in any portion subsequent to the manifold portion, thereby obviating the occurrence of afterbum noises. Thus, the present invention can reduce the size of the air pump as well as the power consumption of the engine.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic representation of the exhaust emission purifying device according to an embodiment of the present invention as applied to an automotive gasoline engine.

FIG. 2 is a cross-sectional view showing the essential part of the exhaust emission purifying device shown in FIG. 1.

FIG. 3 is a graph for illustrating the operating characteristic of the air pump applied to the known air injection type exhaust emission purifying device.

FIG. 4 is a side view of the accelerator pedal used with the present invention.

FIG. 5a is a diagrammatic representation of the exhaust emission purifying device according to another embodiment of the present invention.

FIG. 5b is a cross-sectional view showing the essential part of the FIG. 5a embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention willnow be described by way of example with reference to the accompanying drawings.

Referring to FIGS. 1 and 2, there is shown an engine 1 provided with an air pump 2 which is driven from the crankshaft pulley 3 of the engine 1 through a belt 3. The air pump 2 has its outlet connected to an air distributor 5 through a secondary air supply hose 4. The air distributor 5 is connected to a secondary air injection tube 6 disposed in an exhaust port 7 formed around the exhaust valve 8 of each cylinder 8. The secondary air injection tube 6 has its free end disposed adjacent to the exhaust valve 8. The exhaust port 7 terminates in an exhaust manifold 9 connected to an exhaust pipe 10', and the exhaust manifold 9 is provided with a suitable number of sparking plugs 11. A sparking voltage is applied to the sparking plugs 11 by a sparking voltage generator 12 connected with a power source such as battery 13. The air pump 2 has a relief valve 2a provided at the outlet thereof and adapted to open when the pressure of the air discharged from the air pump 2 reaches a predetermined level or higher. A microswitch 14 and an accelerator pedal 15 are provided as will be described.

In operation, if the engine 1 is started so that the air pump 2 is driven from the crankshaft pulley 3 through the belt 3, the air discharged from the air pump 2 passes through the secondary air supply hose 4 to the air distributor 5, from which the air is injected through the secondary air injection tube 6 into the exhaust port 7 of each cylinder 8. As a result, the exhaust valve 8 is opened in the exhaust process of the engine 1, and when the hot exhaust gases produced immediately after combustion are admitted into the exhaust port 7, these exhaust gases are mixed with the secondary air that has been injected through the secondary air injection tube 6 into the exhaust port 7, thereby causing an oxidizing reaction. The carbon monoxide contained in such exhaust gases has the highest density during the idling of the engine 1, say, usually 6 to 7 percent or sometimes as high as 10 percent or more, for this reason a greater quantity of secondary air must be supplied from the air pump 2 in such engine operating condition that in any other engine operating condition. During the idling of the engine, if the quantity of secondary air supplied from the air pump 2 is substantially equal to the quantity of air actually required to bring about the said oxidizing reaction or the theoretically required quantity of air, then the secondary air and exhaust gases supplied into the exhaust port 7 by injection are not mixed together enough to achieve sufficient oxidation. The exhaust gases, however, are better mixed with the secondary air in the exhaust manifold portion and the resultant mixture has a high temperature due to the partial oxidizing reaction due to the exhaust gases. Thus, the hot air-gas mixture is fired by the sparking plugs 11 as it passes the manifold 9, and the combustion of the mixture provided by such firing expedites a higher degree of oxidation.

Especially under cold weather conditions, if the accelerator pedal is released from depression while the engine in warmed up, the intake gas to engine becomes a greatly enriched mixture as described previously, to thereby cause misfiring in each cylinder 8, and the unburned gases are mixed with the secondary air in the exhaust port 7 to provide an air-gas mixture which is ready to burn.

With the described device of the present invention, the sparking plugs 11 provided in the manifold 9 fire and burn the readily burnable mixture each time and immediately it is produced. This means that no such gas-air mixture ready to burn is accumulated in any part subsequent to the exhaust manifold 9, and accordingly no explosive combustion is produced in the exhaust manifold 9 and exhaust pipe 10 as mentioned above even if firing is again started in the cylinders 8 of the engine 1. Further, the firing and combustion of the gas-air mixture in the exhaust manifold 9 by the sparking plugs 11 can improve the exhaust emission purifying performance more than in the case where use is made only of an anti-afterburn valve. Moreover, even if the anti-afterbum valve is eliminated and air is not supplied to the air intake system of the engine 1 during the deceleration to thereby cause misfiring therein, the firing and combustion of the gas mixture provided by the sparking plugs 11 in the exhaust manifold 9 can achieve the prevention of afterburn noises and purification of the exhaust emissions at the same time. Thus, the firing of the gas mixture achieved by the sparking plugs 11, unlike the anti-afterburn valve, does not deteriorate the purifying performance whether the engine is cold or hot. In this way, the present invention also has an excellent merit in that the problem of afterburn noises which has existed in the air injection type exhaust emission purifying device of the prior art can be completely solved without sacrificing the performance of purification.

The location and number of the sparking plugs 1 1 are determined by the shape of the exhaust manifold 9. If the exhaust manifold employed is large in volume and has its outer surface covered with a heat-insulating material to maintain the temperature of the gases therein, then the sparking plugs will of course achieve enhanced firing performance and accordingly improve the purifying performance.

On the other hand, however, there is still a problem that the exhaust gases are difficult to be fired and combusted by the sparking plugs except during the idling and especially deceleration of the engine when the exhaust gases contains a high density of harmful unburned emission. In other words, difficulty in firing the exhaust gases is encountered during the normal and high-speed running operations when the exhaust gases contain a low density of harmful unburned emission. For this reason, using sparking plugs suitable for all modes of engine operation is undesirable from the viewpoint of the fatigue and power consumption of the sparking plugs.

To solve this problem, the power switch of the sparking plugs may be provided in the lower pedal of the double-pedal accelerator so that the power switch is closed only when the upper pedal of the double-pedal accelerator has no pressure applied thereto. The deceleration of the engine can be detected by one of various known means such as the increase in the intake load pressure or the return of the accelerator link, but if use is made of sparking plugs provided in the exhaust manifold portion and actuated for deceleration, the compensation for any delay in the start of the sparking plugs can be effectively achieved by detecting the initial motion of that artificial actuation which is directed to decelerate the engine. For this purpose it is the most appropriate to detect the decrease in the pressure applied to the accelerator pedal. Therefore, if the accelerator pedal takes a double-pedal construction consisting of an upper and a lower pedal and the lower pedal is provided with a power switch for the sparking plugs so that the power switch is open only when the upper pedal is depressed by the drivers foot, then the power switch is closed to pass a current to the sparking plugs when the pressure applied to the accelerator pedal is decreased. Thus, when the throttle valve is closed to initiate the deceleration of the engine, the sparking plugs are sufficiently brought into their operative condition to completely prevent the occurrence of any afterburn and at the same time the working life of the sparking plugs is increased as well as the power consumption is economized, because the current flow to the sparking plugs is cut off during the acceleration and cruising-speed operation of the engine.

As shown in FIG. 4, the accelerator pedal 15 used with the present invention is of a double-pedal construction consisting of a lower pedal 17 for directly driving an accelerator lever 16, and an upper pedal 19 pivotally connected to the lower pedal 17 by means of pivot shaft 18. The lower pedal 17 is provided with a microswitch 14. Between the-pedals l7 and 19 a spring 20 provides a clearance sufficient to allow the switch knob 21 of the microswitch 14 to intervene therebetween. Lead wires 22 and 23 are provided to electrically connect the microswitch 14 with the high-voltage generator 12 and power source 13. The microswitch 14 is adapted to close when the switch knob 21 is not actuated, and to open when the switch knob 21 is depressed.

In the described arrangement, the pressure applied to the upper pedal 19 of the double-pedal accelerator 15 by the drivers foot is decreased or the pressure is released from the upper pedal 19 during the deceleration and idling operations of the engine, and this causes the upper pedal 19 to be returned by the spring 20 to thereby release the switch knob 21 of the microswitch 14. As the result, the microswitch 14 is closed to connect the high-voltage generator 12 with the power source 13, whereby the sparking plugs 11 are energized to fire and burn the gases ready to burn discharged into the exhaust manifold 9. When the drivers foot rests on the upper pedal 19, the microswitch 14 is opened to electrically disconnect the high-voltage generator 12 with the power source 13 to thereby stop the firing action of the sparking plugs 11.

During continuous high-load operation of the engine, the exhaust manifold is usually overheated irrespective of the presence of the device according to the present invention and this may lead to the danger of burning off the sparking plugs provided in the manifold and the high-voltage lead wires connected to the sparking plugs. Such danger can be obviated by blowing part of the air from the air pump to the sparking plugs. The air for cooling the sparking plugs is provided by causing the air discharged through the relief valve located in the outlet portion of the air pump and/or the air discharged through the relief hole for pump-leakage air to be directed through rubber hoses or like means and blown to the sparking plugs in the exhaust manifold portion. Thus, the exposed portion of the sparking plugs and the connecting portion thereof to the high-voltage lead wires are caused to be cooled by the cooling air and can be protected from the danger of having their insulating coatings being burnt off even if the exhaust manifold will become to overheated temperature.

FIGS. 5a and 5b show another embodiment of the present invention, in which like parts are designated by like numerals used in FIG. 1. In this alternative embodiment, the air relief valve 2a of the air pump 2 opens when the pump increases its revolution until the air pressure discharged therefrom reaches a predetermined level or higher. The air discharged from the relief valve 2a is directed through a hose 24 so as to be blown to the sparking plugs 11. An overheated temperature of the exhaust manifold 9 means a high-load, high-speed operation of the engine 1 and accordingly a high-discharge pressure of the air pump 2, which in turn means that the air from the relief valve 2a is effectively cooling the sparking plugs 11 to protect the plugs 11 and high-voltage lead wires 15 from being burnt off.

If a rotary vane pump is used as the air pump, the cooling air may be provided not only by the air from the relief valve 2a but also by the leakage air taken out through the leakage hole in the pump and possessing a certain degree of pressure. The latter air also tends to increase in proportion to the discharge pressure and number of revolutions of the air pump 2 and serves to help the cooling function effectively. If two hoses are provided so as to utilize air both from the relief valve and relief hole of the pump, the sparking plugs may no doubt be cooled further effectively. It is also possible that the oxidizing air directed to the exhaust port 7 be utilized for cooling purposes.

In the above-described embodiments, the sparking plugs 11 may be heating elements such as heating wires or the like and disposed in the exhaust pipe 10 adjacent to the exhaust manifold 9 instead of being disposed in the manifold itself.

What is claimed is:

1. An exhaust emission purifying device for an internal combustion engine having exhaust ports and an exhaust manifold; and device comprising an air pump driven by said engine;

means for discharging air supplied by said air pump into said exhaust ports of said engine;

at least one spark plug provided in said exhaust manifold of said engine for producing sparks within said exhaust manifold;

means for energizing said spark plug to produce said sparks;

and

means for conducting a part of the air from said air pump on to said spark plug to cool said spark plug.

2. An exhaust emission purifying device as defined in claim 1, further comprising:

LII

means for energizing said spark plug to produce said sparks, said energizing means being operative to energize said spark plug only when said engine is in idling condition and when said engine is in deceleration.

3. An exhaust emission purifying device as defined in claim 2, wherein said energizing means comprises:

an auxiliary pedal coupled with an accelerator pedal for said engine so that the accelerator pedal can be depressed only after said auxiliary pedal is depressed; and

an electric switch coupled with said auxiliary pedal so as to be opened when said auxiliary pedal is depressed;

said switch being connected with said spark plug so as to energize said spark plug when said switch is closed.

4. For an internal combustion engine which includes at least one cylinder connected to an exhaust manifold via exhaust valve means, an exhaust emission purifying device comprising:

an air pump driven from an engine for discharging air into the exhaust port of each cylinder of said engine, and at least one sparking plug provided in the manifold portion of said device, said sparking plug being electrically energized to produce sparks within said exhaust manifold;

a double-type accelerator comprising an upper, auxiliary pedal resiliently spaced above a lower, main pedal when the engine is idling or decelerating, but is depressed operatively against the lower, main pedal when the engine is being accelerated or run at faster-than-idling speed;

an electrical switch having a first, normal mode wherein said switch electrically connects said sparking plug to a source of electric power and a second mode wherein said sparking plug is disconnected from the source of electric power;

said electrical switch having an actuator disposed to be actuated to temporarily change said switch from the first to the second mode'thereof only when said upper, auxiliary pedal is depressed toward said lower, main pedal.

5. For an internal combustion engine having at least one cylinder connected to an exhaust conduit, an exhaust valve means interposed between the cylinder and the exhaust conduit; control means operatively connected to said engine for accelerating said engine when actuated in one sense, for permitting said engine to decelerate when actuated in an opposite sense, for permitting said engine to return to and remain at idle when actuated to a null position, and for running said engine at a substantially faster-than-idle speed when maintained deflected from said null position;

an exhaust emission purifying device, comprising:

air pumping means for supplying pressurized air to said exhaust conduit;

selectively operable, combustion inducing heating means disposed on said exhaust conduit where said pressurized air is supplied to said exhaust conduit, for inducing combustion of the mixture defined upon mixing of exhaust emission from said cylinder with said pressurized air;

sensing means responsive to (a) actuation of said control means in said one sense, (b) actuation of said control means in said opposite sense, (c) actuation of said control means to and disposition of said control means at idle; and (d) maintenance of said control means substantially deflected from said null position thereof; said sensing means being operatively connected to said selectively operable combustion inducing heating means for operating the heating means to combust said mixture (a) when said control means is actuated in said opposite sense, and (b) when said control means is in said null position thereof, and for terminating said operating (a) when said control means is actuated in said one sense; and (b) when said control means is being maintained substantially deflected from said null position.

6. The exhaust emission purifying device of claim 5 wherein the heating means comprises a sparking device disposed in the exhaust conduit and means operatively connected to said sparking device for causing said sparking device to emit sparks within said exhaust conduit.

7. The exhaust emission control device of claim 6 wherein the air pumping means is configured for connection to the engine for operation thereby in direct relation to the running of the engine.

8. The exhaust emission control device of claim 7 wherein the air pumping device further includes a pressurized air delivery conduit connected thereto and supplied thereby, said pressurized air delivery conduit having means defining an outlet disposed adjacent the sparking device, exteriorly of the exhaust conduit for transferring heat from said sparking device.

9. The exhaust emission control device of claim 8 further including a normally closed valve interposed between the air pumping device and the pressurized air delivery conduit; and valve control means responsive to the running of the engine, said valve control means being operative to open said valve means when the engine is being run faster than a predetermined threshold level.

10. The exhaust emission control device of claim 9 wherein the air pumping means is a rotary vane pump having a leakage hole for emitting pressurized air in a varying amount which varies directly with the discharge pressure and number of revolutions per unit time of the rotary vane pump, said pressurized air delivery conduit being connected to the pump via hole for receiving the pressurized air to be delivered thereby from said hole.

11. The exhaust emission control device of claim 5, wherein the heating means is disposed adjacent the exhaust valve means. 

1. An exhaust emission purifying device for an internal combustion engine having exhaust ports and an exhaust manifold; and device comprising an air pump driven by said engine; means for discharging air supplied by said air pump into said exhaust ports of said engine; at least one spark plug provided in said exhaust manifold of said engine for producing sparks within said exhaust manifold; means for energizing said spark plug to produce said sparks; and means for conducting a part of the air from said air pump on to said spark plug to cool said spark plug.
 2. An exhaust emission purifying device as defined in claim 1, further comprising: means for energizing said spark plug to produce said sparks, said energizing means being operative to energize said spark plug only when said engine is in idling condition and when said engine is in deceleration.
 3. An exhaust emission purifying device as defined in claim 2, wherein said energizing means comprises: an auxiliary pedal coupled with an accelerator pedal for said engine so that the accelerator pedal can be depressed only after said auxiliary pedal is depressed; and an electric switch coupled with said auxiliary pedal so as to be opened when said auxiliary pedal is depressed; said switch being connected with said spark plug so as to energize said spark plug when said switch is closed.
 4. For an internal combustion engine which includes at least one cylinder connected to an exhaust manifold via exhaust valve means, an exhaust emission purifying device comprising: an air pump driven from an engine for discharging air into the exhaust port of each cylinder of said engine, and at least one sparking plug provided in the manifold portion of said device, said sparking plug being electrically energized to produce sparks within said exhaust manifold; a double-type accelerator comprising an upper, auxiliary pedal resiliently spaced above a lower, main pedal when the engine is idling or decelerating, but is depressed operatively against the lower, main pedal when the engine is being accelerated or run at faster-than-idling speed; an electrical switch having a first, normal mode wherein said switch electrically coNnects said sparking plug to a source of electric power and a second mode wherein said sparking plug is disconnected from the source of electric power; said electrical switch having an actuator disposed to be actuated to temporarily change said switch from the first to the second mode thereof only when said upper, auxiliary pedal is depressed toward said lower, main pedal.
 5. For an internal combustion engine having at least one cylinder connected to an exhaust conduit, an exhaust valve means interposed between the cylinder and the exhaust conduit; control means operatively connected to said engine for accelerating said engine when actuated in one sense, for permitting said engine to decelerate when actuated in an opposite sense, for permitting said engine to return to and remain at idle when actuated to a null position, and for running said engine at a substantially faster-than-idle speed when maintained deflected from said null position; an exhaust emission purifying device, comprising: air pumping means for supplying pressurized air to said exhaust conduit; selectively operable, combustion inducing heating means disposed on said exhaust conduit where said pressurized air is supplied to said exhaust conduit, for inducing combustion of the mixture defined upon mixing of exhaust emission from said cylinder with said pressurized air; sensing means responsive to (a) actuation of said control means in said one sense, (b) actuation of said control means in said opposite sense, (c) actuation of said control means to and disposition of said control means at idle; and (d) maintenance of said control means substantially deflected from said null position thereof; said sensing means being operatively connected to said selectively operable combustion inducing heating means for operating the heating means to combust said mixture (a) when said control means is actuated in said opposite sense, and (b) when said control means is in said null position thereof, and for terminating said operating (a) when said control means is actuated in said one sense; and (b) when said control means is being maintained substantially deflected from said null position.
 6. The exhaust emission purifying device of claim 5 wherein the heating means comprises a sparking device disposed in the exhaust conduit and means operatively connected to said sparking device for causing said sparking device to emit sparks within said exhaust conduit.
 7. The exhaust emission control device of claim 6 wherein the air pumping means is configured for connection to the engine for operation thereby in direct relation to the running of the engine.
 8. The exhaust emission control device of claim 7 wherein the air pumping device further includes a pressurized air delivery conduit connected thereto and supplied thereby, said pressurized air delivery conduit having means defining an outlet disposed adjacent the sparking device, exteriorly of the exhaust conduit for transferring heat from said sparking device.
 9. The exhaust emission control device of claim 8 further including a normally closed valve interposed between the air pumping device and the pressurized air delivery conduit; and valve control means responsive to the running of the engine, said valve control means being operative to open said valve means when the engine is being run faster than a predetermined threshold level.
 10. The exhaust emission control device of claim 9 wherein the air pumping means is a rotary vane pump having a leakage hole for emitting pressurized air in a varying amount which varies directly with the discharge pressure and number of revolutions per unit time of the rotary vane pump, said pressurized air delivery conduit being connected to the pump via hole for receiving the pressurized air to be delivered thereby from said hole.
 11. The exhaust emission control device of claim 5, wherein the heating means is disposed adjacent the exhaust valve means. 